Showing posts with label oncological control. Show all posts
Showing posts with label oncological control. Show all posts

Tuesday, August 30, 2016

Safety limits of SBRT dose escalation

In a recent commentary, we saw that the lack of a standard of care for SBRT dose escalation may put patients at risk when dose limits are pushed beyond what is customarily considered effective and safe. Hannan et al. have now published their efficacy findings. Further details of the IRB-approved clinical trial specs are available here.

Between 2006 and 2011, the researchers at several institutions conducted a dose escalation trial utilizing SBRT on 91 men treated for low and intermediate risk prostate cancer. Among those men:
  • ·      64% were intermediate risk, defined as:

o   Either GS 6 and PSA between 10 and 20 ng/ml , or
o   GS 7 with PSA≤ 15 ng/ml and clinical stage ≤ T2b
  • ·      36% were low risk by the NCCN definition.

All patients received 5 treatments or fractions. The first 15 patients were treated with 45 Gy, the next 15 with 47.5 Gy, the next 15 with 50 Gy. Because that last group did not exhibit their predefined “maximally tolerated dose” in the short term, an additional 47 patients also received the 50 Gy dose.

The cancer control was excellent. At 5 years after treatment:
  • ·      98.6% were free from biochemical failure
  • ·      100% were free from metastases
  • ·      None had died of prostate cancer
  • ·      Overall survival was 89.7%

Toxicity was another matter. There were no reports of serious acute urinary toxicity. However, late-term urinary toxicity of grade 3 or greater was reported in 5.5% of patients. For the purposes of their analysis, acute toxicities were those observed within 9 months of treatment, and late-term toxicities were those observed between 9 and 18 months.

Rectal toxicity was reported in detail earlier by Kim et al. and merit a closer look:
  • ·      Among those who received 45 Gy there was no serious (grade 3 or higher) acute or late term toxicity.

o   No acute grade 2 toxicity was observed.
o   Late-term grade 2 toxicity was observed in 1 patient (of 15).
  • ·      Among those who received 47.5 Gy there was no serious (grade 3 or higher) acute or late term toxicity.

o   Acute grade 2 toxicity was observed in 4 of 15 patients (27%)
o   Late-term grade 2 toxicity was observed in 5 of 15 patients (33%).
  • ·      Among the 61 patients who received 50 Gy there was:

o   One case of serious (grade 3) acute toxicity and one case of life-threatening (grade 4) acute toxicity.
o   3 cases (5%) of serious (grade 3) late-term toxicity and 2 cases (3%) of life-threatening (grade 4) late-term toxicity.
o   2 of the patients developed rectourethral fistulae, and 5 required diverting colostomies.


We note that even at the lowest dose level given in this trial (45 Gy), they were delivering much more than the customary SBRT dose of 36.25 Gy. Because this study began with such a high dose, it did not succeed in its objective of finding an optimal dose. It did, however, find the dose that created dose-limiting toxicity. At 50 Gy, they were delivering a dose that is bioequivalent to more than twice the customary and safe IMRT dose (80 Gy in 40 fractions). This is especially troubling when we realize that 36% were low-risk patients who might have delayed treatment with active surveillance.

There are many aspects of this study that are hard to understand. It’s hard to understand why they didn’t start at a more reasonable dose level. Dr. Alan Katz reported excellent cancer control with extremely low toxicity using only 35 Gy (see this link). With the sharp increase in acute grade 2 toxicities at 47.5 Gy, it’s hard to understand why the researchers did not pull the plug before patients were seriously harmed. It’s also hard to understand how the internal review board (IRB) did not question the ethics of this study.

(Update 2/6/2019) In a small (n=26) prospective dose-finding study of 40 Gy (n=9), 45 Gy (n=10) and 50 Gy (n=7) among low and intermediate risk patients, Potters et al. reported freedom from biochemical failure of 92%, 100% and 100% respectively with 67 months of follow-up. There were no Grade 3 toxicities, and toxicity was about equal in all groups. Quality of life returned to baseline in all groups within 2 years.


We have observed (see this link) that there is a lot more to SBRT safety than simply setting the prescribed dose. Careful planning, image guidance and accurate delivery are equally important. In the right hands, SBRT is among the safest and most effective of all radiation therapies, with excellent convenience and relatively low cost. In fact, I chose it for myself.

Is there an optimal treatment schedule for high dose rate brachytherapy?

Protocols for high dose rate brachytherapy (HDR-BT) monotherapy vary. In recent years, practitioners have adopted various schedules for patient and physician convenience. Jawad et al. reported on the HDR-BT experience at William Beaumont Hospital. They treated 494 favorable risk patients using three different treatment schedules. Their definition of “favorable risk” was a Gleason score ≤7 and stage≤T2b and PSA≤15 ng/ml. The 3 treatment schedules they utilized, the number of patients who received each, and the relative biologically effective dose  (BED) were as follows:
  1. 38 Gy in 4 fractions (n=319) – 1.29 relative BED 
  2. 24 Gy in 2 fractions (n=79) – 1.00 relative BED 
  3. 27 Gy in 2 fractions (n=96) – 1.25 relative BED
Dose schedules #1 and #3 delivered much higher relative dose compared to dose schedule #2. The questions addressed by the study are whether the higher dose is justified by greater cancer control, and whether dose increased at the expense of increased side effects.

After 5.5 years median followup for schedule #1, 3.5 years for schedule #2, and 2.5 years for schedule #3, the toxicity outcomes were as follows:
  • No difference in clinical outcomes (cancer control) among the 3 treatment schedules.
  • Acute (appearing in less than 6 months) and chronic (appearing 6 months or more after treatment) grade ≥2 genitourinary (GU) and gastrointestinal (GI) side effects were similar for all treatment schedules.
  • Grade 2 acute GU toxicities:
o   Frequency/urgency: 14%
o   Dysuria (painful urination): 6%
o   Retention: 7%
o   Incontinence: 1.5%
o   Hematuria (blood in urine): 1.5%
  • ·      Grade 2 chronic GU toxicities:
o   Frequency/urgency: 20%
o   Dysuria (painful urination): 7%
o   Retention: 4% (Urethral stricture: 2%)
o   Incontinence: 2%
o   Hematuria (blood in urine): 7%
  • ·      There was minimal grade 3 GU toxicity
  • ·      Grade 2 acute GI toxicities:
o   Diarrhea: 1%
o   Rectal pain/tenesmus: <1%
o   Rectal bleeding: 0%
o   Proctitis: <1%
  • ·      Grade 2 chronic GI toxicities:
o   Diarrhea: 1%
o   Rectal pain/tenesmus: 0.5%
o   Rectal bleeding: 2%
o   Proctitis: 1%
  • ·      No Grade 3 or higher GI toxicity
  • ·      Time to maximal appearance of symptoms was similar across treatment schedules
  • ·      They did not report ED rates, which are typically low for HDR-BT.
Given the equivalence of cancer control and toxicity with treatment schedule, and the lack of any effect due to increasing the biologically equivalent dose, there seems to be little basis, other than cost and convenience, for choosing among these treatment schedules, at least with the available follow-up reported here.

Aspects of treatment scheduling that affect the convenience of HDR-BT are the number of implantations of the catheters, and the time frame in which the fractions are delivered.  William Beaumont Hospital uses a single implantation of catheters for all treatment schedules. Schedule #1 involves a longer (overnight) hospital stay because they wait for several hours between fractions for healthy tissue to recover. It also means that anesthesia must be administered over a longer period.

The California Endocurietherapy Center at UCLA has typically used a different protocol. They deliver 42 Gy in 6 fractions, with 3 fractions delivered one week and 3 fractions delivered a week later. This involves 2 overnight hospital stays, with anesthesia each time. Recently, they added a protocol where they deliver 27 Gy in 2 fractions (similar to schedule #3), but those fractions are still inserted a week apart. While this is certainly a cost reduction for the patient, who can now be treated as an outpatient, the patient is inconvenienced by having to go through the full procedure twice. It is a convenience for the treatment team that no longer has to attend the patient over an extended timeframe.


The William Beaumont Hospital experience demonstrates that HDR-BT treatment schedules can be constructed so as to lower costs and increase convenience for patients and doctors, without sacrificing cancer control or quality of life.

Thursday, August 25, 2016

Can a man be too young for active surveillance?


There is a “conventional wisdom” that active surveillance (AS) is only for older men, and that younger men are better off having immediate radical treatment, typically prostatectomy (RP). By “better off” we mean that there is a better chance at cancer control, or that the side effects of treatment, particularly incontinence and impotence, will be milder if treated earlier. Let’s turn a spotlight on that conventional wisdom, and see if it holds up under scrutiny.

The screening protocol for men under 50 years of age that is advocated by Memorial Sloan Kettering (see this link and this one), and recently discussed here, has important implications for active surveillance. Autopsy studies have demonstrated prostate cancer incidence of 20-30% in men under 50, mostly low grade and indolent. With increased screening of this young cohort, there will be an increase in the current incidence rate (now at about 10%). These men will increasingly be urged by their urologists to seek radical treatment, primarily surgery. If their screening protocol is widely adopted, there is great danger of over-treatment for this age group.


Oncological Control

With up to 20 years of follow-up, the Klotz Active Surveillance Trial has demonstrated the safety of that protocol. Klotz reported that of the 993 patients, there were only 15 deaths (1.5%) due to prostate cancer. When he pooled together several active surveillance studies, he found that the combined disease-specific survival rate was 99.7%. A Gleason score of 8-10 on confirmatory biopsy and a PSA doubling time of less than 3 years were associated with mortality, indicating the importance of close monitoring and follow-up biopsies on any active surveillance protocol.

It is worth noting how long men entering the Klotz study were able to stay on active surveillance before their progression characteristics indicated that radical treatment was required. Most of the progression was found in the first 5 years after entering the program, and reached a plateau by 15 years.

Time on AS
Percent for whom no treatment was recommended
5 years
75.7%
10 years
63.5%
15 years
55.0%
20 years
55.0%


Age was not a risk factor for prostate cancer mortality. Klotz said, “Younger patients were not at increased risk of prostate cancer mortality.” In fact, in younger men, the risk of non-prostate cancer mortality was almost six times higher than the rate of prostate cancer mortality.

It’s important to understand how slowly low-risk prostate cancer typically progresses in young men, even without active surveillance; that is, even without an intention to treat if the cancer progresses. Based on the Memorial Sloan Kettering Nomogram, we can see that for a 45 year-old man in excellent health diagnosed with a Gleason score of 3+3, PSA of 4 ng/ml, and nothing felt on a digital rectal exam, he has a zero chance of dying of prostate cancer in the next ten years, and a 4% chance of dying of something else. Even if he lets it go for 15 years, he only has a 3% chance of dying of prostate cancer, and an 8% chance of dying of something else.

It has been observed that there are rare and virulent forms of prostate cancer that are more prevalent in men under 50, and particularly among younger African-American men (see this link and this link). This is irrelevant to the discussion of active  surveillance  because those men will seldom be good  candidates for active surveillance from the outset. And if they do get in, clinical progression will be noticed in any active surveillance protocol at a very early time. Still, it is a reasonable precaution to screen men under 50 for genetic markers when there is a family history of early prostate cancer; for example, Oncotype Dx, Prolaris, TMPRSS2-ERG fusion, PTEN loss, or BRCA2 mutations.

Advancing age at the time of diagnosis is associated with a worse prognosis. In an analysis of 205,551 cases in the SEER database (see this link), 15-year prostate cancer mortality rates increased steadily with age at diagnosis.

Age Group
15-year PC mortality
≤50
2.3%
51-60
3.4%
61-70
4.6%
≥71
6.3%

Once again, this observation is irrelevant to a discussion of active surveillance. Age was not found to be a prognostic factor after accounting for Gleason score, tumor stage and PSA. The higher risk older men would probably not meet the entry criteria for active surveillance (although, depending on co-morbidities, they may be good candidates for watchful waiting). Those older men with more virulent disease that do get into an AS program would most likely be soon found to progress and be safely treated in time.

Based on oncological prognosis, younger age should not be used to decide between active surveillance and radical therapy.

Continence

An argument for treatment for younger men has been that there is a higher chance of continence preservation after surgery among younger men who already have better continence. Let’s see what the real-world numbers look like.

Continence naturally declines with age. Population-based continence statistics on younger men is scarce, but we can reasonably assume that moderate to severe incontinence is a rare occurrence in a 45 year-old man, and for our purposes, let us suppose that a 45 year old, just diagnosed with low-risk prostate cancer, is fully continent. What decision maximizes his lifetime expected continence?

Age
A. No natural moderate or severe incontinence
B. Expected lasting continence for men treated at that age
C. Percent losing continence due to RP at that age
D. Probability of staying on AS if started at 45
E. Expected loss of continence due to decision to initially have RP rather than AS
F. Life expectancy (years)
45
100%
80%
20%
100%
20%
34
50
92%*
79%
13%
76%
10%
30
55
84%
74%
10%
64%
6%
25
60
81%
70%*
11%
55%
6%
21
65
79%
66%
13%
55%
7%
18
70
74%
63%
11%
55%*
6%
14
75
74%*
59%
15%
55%*
8%
11

Sources:
B.     Younger cohort is from Johns Hopkins prostatectomy patients, older cohort is from University of Chicago: http://www.jurology.com/article/S0022-5347(06)01930-6/abstract http://www.jurology.com/article/S0022-5347(10)00017-0/abstract
C.     Column A – Column B
D.    Klotz, assuming plateau continues
E.     Column C x Column D
F.     Social Security actuarial tables
* extrapolated figures

Our fully continent 45 year-old man has about an 80% chance of retaining his continence if he has an immediate RP.  So, about 20% of 45 year-old men will lose continence if they decide for RP rather than AS. Those 20% will live with that loss of continence for 34 years.

If he chooses AS instead of RP, what happens in the next 5 years? He has some small natural deterioration of continence, roughly an 8% expected loss. If he has an RP 5 years from now, his expected continence is about the same at 79%. Therefore, his net expected loss of continence will be 13% if he remains on AS for the full 5 years. But he has only a 76% chance of staying on AS for the first 5 years. Therefore, his expected loss of continence due to the decision to go on AS at 45 and get treated at 50 is 10% - only half as much as if he had the RP at 45. And he will expect to live with that incontinence for fewer years.

If he chooses AS at 45 and manages to stay on it for the next 25 years without treatment (a 55% probability), his expected loss of continence (incorporating the probability of being able to go that long without treatment) is minimized, at only 6%. And he will only have to suffer the loss for 14 years.

With respect to preserving continence, the 45 year old man is better off going on AS and staying on it as long as he can. What’s more, it can be easily shown with a similar continence analysis that a man diagnosed with low risk prostate cancer at any age, is better off choosing AS over immediate treatment.

We have ignored the stress incontinence that persists even after “full” continence is restored. 34 years is a long time to worry about leakage every time a man coughs, sneezes, laughs or plays sports.

Potency Preservation

Potency is better preserved by prostatectomy while the patient is younger and fully potent. Is our 45-year old man, newly diagnosed with low risk prostate cancer and fully potent, better off having a prostatectomy immediately, or choosing AS? Let’s run the numbers.


Age
A. Expected potency without prostatectomy
B. Expected lasting potency for men treated at that age
C. Percent losing potency due to RP at that age
D. Probability of staying on AS if started at 45
E. Loss of potency due to decision to initially have RP rather than start with AS
F. Life expectancy (years)
45
100%
55%
45%
100%
45%
34
50
94%*
49%*
45%
76%
34%
30
55
87%
43%
44%
64%
28%
25
60
82%
35%*
47%
55%
26%
21
65
74%
27%
47%
55%
26%
18
70
60%
18%*
42%
55%*
23%
14
75
45%
8%
37%
55%*
20%
11


Sources:
B.     http://jama.jamanetwork.com/article.aspx?articleid=1104401 Supplemental content: eTable3 (97% had nerve-sparing surgery)
C.     Column A – Column B
D.    Klotz, assuming plateau continues
E.     Column C x Column D
F.     Social Security actuarial tables
* extrapolated figures

Our fully potent 45 year-old man has a 55% chance of retaining his potency if he has an immediate RP.  So, about 45% of 45 year-old men will lose potency if they decide for RP rather than AS. Those 45% will live with that impotence for 34 years.

If he chooses AS instead of RP, what happens in the next 5 years? He has some small natural deterioration of potency, roughly a 6% expected loss. If he has an RP 5 years from now, his expected potency will be a less too, at 49%. Therefore, his expected loss of potency nets out exactly the same (at 45%) if he remains on AS for the full 5 years. But he has only a 76% chance of staying on AS for the first 5 years. Therefore, his expected loss of potency due to the decision to go on AS at 45 and get treated at 50 is 34% - 11 percentage points less than if he had the RP at 45. And he will expect to live with that impotence for fewer years.

If he chooses AS at 45 and manages to stay on it for the next 25 years without treatment (a 55% probability), his expected loss of potency (incorporating the probability of being able to go that long without treatment) is only half of the expected loss due to immediate treatment, at only 23%. And he will only have to suffer the loss for 14 years.

With respect to preserving potency, the 45 year-old man is better off going on AS and staying on it as long as he can. What’s more, it can be easily shown with a similar potency analysis that a man diagnosed with low-risk prostate cancer at any age, is better off choosing AS over immediate treatment.

This analysis ignores other important sexual side effects that would certainly weigh against immediate prostatectomy. Those sexual side effects include loss of penile length and girth, climacturia, Peyronie’s, venous leak, dry orgasms, anorgasmia, and dysorgasmia. Baseline erectile function is seldom restored fully. Loss of libido and psychologically induced loss of erectile function and depression are common results of all the aforementioned. Even when erectile function can be induced chemically, there is significant cost attached to 34 years of ED medicines or injections.

Radiation

The choice is not nearly as clear when the decision is between AS and radiation therapy (either external beam or brachytherapy) for young low-risk patients. Incontinence is a very low probability side effect of radiation, and potency preservation is much better within every age group, chronic side effects of any kind are rare with modern technology. It is often argued that we don’t know how cancer control will change with 25+ years of follow-up after dose-escalated radiation. As we have seen (see this link), recurrence rates did not reach a plateau for RP or IMRT; however, if we were to examine low-risk patients only, it is likely that long-term results would be more stable for both surgery and radiation.

It is worth mentioning that there is another bit of “conventional wisdom” that does not hold up under scrutiny of the medical evidence. Many urologists incorrectly state or imply that the side effects of radiation are progressive and won’t show up for many years. Under that scenario, a 45 year-old man treated with radical radiation would eventually wind up with impotence 10 years later, as well as urinary and rectal problems. The PROSTQA study (see this link) of men treated in 1999 showed that most of the radiation-induced toxicity showed up early, and that much of the “late-term toxicity” observed may actually have been attributable to age, diabetes, and comorbidities (see this link).

The percent experiencing grade 2 or higher urinary toxicities (excluding incontinence) by 5 years, 8 years, and 10 years after treatment was:
  • ·      IMRT: 8.6% at 5 years, 11.2% at 8 years, and 10 years (76% of 10-year total by 5 years)
  • ·      BT: 4.3% at 5 years, 8 years, and 10 years (100% of 10-year total by 5 years)
  • ·      RP: 3.1% at 5 years, 3.7% at 8 years, and 5.5% at 10 years (56% of 10-year total by 5 years)
Ironically, we would conclude  (erroneously) from the above that it is prostatectomy, rather than radiation, that has cumulative urinary side effects that progress most over time.

The percent experiencing grade 2 or higher rectal toxicities by 5 years, 8 years, and 10 years after treatment was:
  • ·      IMRT: 7.8% at 5 years, 8 and 10 years (100% of 10-year total by 5 years)
  • ·      BT: 1.7% at 5 years, 8 years, and 10 years (100% of 10-year total by 5 years)
  • ·      RP: 0% at 5 years, 8 years, and 10 years (100% of 10-year total by 5 years)
We have seen in a previous commentary that erectile dysfunction due to radiation was lower than for RP within every age group, that it occurred within the first 9 months following treatment, and that half of the observed deterioration over time was due to the normal aging process.

The case for active surveillance and against radical treatment at a younger age is less convincing if radiation is the treatment of choice. It is for currently mostly a moot point because younger low-risk patients are seldom offered radiation therapy.

Conclusions

I have been personally influenced by the testimony of a 45 year-old man in my prostate cancer support group who was inconsolable and under treatment for suicidal ideation after the loss of continence and potency. Younger men who are single and suddenly find themselves to be impotent and incontinent often despair of finding a mate, and younger men who are married sometimes find their marriages on shaky ground.

It is also important to remember that the longer one is able to stay on AS, the higher the probability a cure will emerge from all the research now in the field. Already it seems that 5ARis (Proscar or Avodart) may delay or even reverse progression in low risk PC. There are a number of hormonal medicines and immunotherapies already being tested that might prove to be even more potent.

AS protocols are already improving, and will continue to be safer. Many institutional protocols now dictate that the first follow-up biopsy should be multiparametric MRI-targeted and/or targeted using a transperineal mapping biopsy. To avoid the danger of excessive biopsies in younger men, many institutions have moved off of the original protocol of annual biopsies. After the first follow-up biopsy, what happens next depends on what happened before. If there were no signs of any progression, the next biopsy can be two years later; after that, maybe 4 years with just an imaging study in between, etc. I know that even Johns Hopkins, which had the strictest AS protocol, relaxed their position on annual biopsies.

We have now seen that starting with AS is a more rational decision than starting with RP for all low risk men. However, the decision is often not a rational one, but is based on fear, traditional “baggage” carried over from other cancers, and the influence of loved ones, relatives and friends. In the end, the young patient must decide what he is most comfortable doing. Maybe it will be AS, maybe SBRT or brachytherapy, maybe surgery. What I am uncomfortable with is his doctor making those life-changing decisions for the patient, and ruling out any options without evidence. The low-risk patient certainly has plenty of time to investigate all options thoroughly for himself before coming to a decision. Taking one’s time often allows one to put emotions in perspective. Leaving all options open until one is ready to decide is the best stance to take. I have only seen treatment regret in men who didn't take the time to do that.